1. Field of the Invention
The invention relates to a high volumetric energy density battery having a light metal anode, a pure silver chromate cathode, and a non-aqueous electrolytic solution. The exothermic reactivity of the anode material with water requires the use of a non-aqueous organic solvent containing a dissolved salt as the electrolytic solution. The electrochemical systems provides a very high volumetric energy density and it is generally preferred to employ the system in small primary batteries. The invention is not limited to any particular battery size or construction nor is it limited to any particular anode material or non-aqueous electrolyte.
2. Description of the Prior Art
The prior art discloses many high energy density battery systems which employ a light metal anode in combination with a non-aqueous organic electrolyte solution. Of particular relevance are U.S. Pat. Nos. 3,658,592 issued to A. N. Dey and assigned to P. R. Mallory & Company, Inc. and 3,853,627, 3,871,915 and 3,970,475 all assigned to Societe des Accumulateurs Fixes et de Traction.
U.S. Pat. No. 3,658,592 discloses a high energy density organic electrolyte battery employing a light metal anode and a metal chromate cathode. The cathode contains a conductive ingredient such as graphite and a polymeric binder such as polytetrafluoroethylene mixed with the metal chromate active material. The cathode composition is molded onto an expanded molded current collector. The patent discloses that the lithium-silver chromate mix cell has a open circuit voltage and an average operating voltage of 3.4, presumably in an electrolyte solution comprising lithium perchlorate (LiClO.sub.4) and tetrahydrofuran. (THF)
U.S. Pat. No. 3,853,627 issued to Gerard Lehmann and Jean-Paul Gabano discloses a high energy density system employing a lithium anode and a silver chromate/graphite cathode. The application states that a mixture of 99% silver chromate and 1% carbon black or any other material insuring a good electrical conductivity of the electrode can be used. The perferred electrolytic solution comprises lithium perchlorate dissolved in a solvent mixture such as tetrahydrofuran and dimethoxyethane. The cells have an average discarge voltage of 2.95 volts across a 9100 ohm resister and a 3.15 volt discharge across a 62000 ohm resister.
U.S. Pat. No. 3,871,915 issued to Alfred Brych discloses a high energy density lithium cell in which the cathode can be a silver chromate mix. The preferred electrolyte comprises lithium perchlorate dissolved in a solvent comprising a mixture of a cyclic ether (dioxolane) and a non saturated cyclic ester (vinylene carbonate). This cell of the example has a cathode mix of silver chromate/graphite/polytetrafluoroethylene and an 80% vinylene carbonate/20% dioxolane electrolytic solution with a lithium anode. The cell has a two voltage plateau discharge across a 300 ohm resister with a voltage plateau of 3 volts and 2.6 volts.
U.S. Pat. No. 3,970,475 issued to Gerard Gerbier and Jean-Paul Rivault discloses a high energy cell in which the positive active material is a mixture of silver chromate and silver powder. The silver powder is added in a proportion to comprise 5 to 30% by weight of the cathode. The patent teaches that since the silver powder is a conductor, it is possible to eliminate the carbon black.
The prior art teaches that silver chromate must be mixed with a conductive material to be utilizable as a cathode material.
It is the object of this invention to provide a high volumeric energy density non-aqueous primary battery having a pure silver chromate cathode. Another object is to provide a non-aqueous primary battery particularly of the button cell construction which does not bulge or expand excessively during discharge. A further object of the invention is to provide a non-aqueous button cell having a cathode material which does not contain a binder or a conductive ingredient such as graphite.